1. Field of the Invention
The present invention relates to a mailing ink, which has a preferable tint as a blue color as well as excellent readability of 2-D (two-dimensional) bar code and can form postal markings. The present invention also relates to an ink tank for mailing, an ink jet recording method for mailing and an ink jet recording apparatus for mailing using this ink.
2. Related Background Art
An ink-jet recording method is a system in which minute droplets of an ink are ejected to apply them to a recording medium such as paper, thereby conducting recording. For example, Japanese Patent Publication No. 61-59911 discloses a thermal ink jet recording method in which electrothermal converters are used as ejection-energy supply means to apply thermal energy to an ink so as to generate bubbles, thereby ejecting droplets of the ink. According to this method, the formation of a high-density multi-orifice in an ink-jet recording head can be realized with ease, and high-resolution and high-quality images can be recorded at high speed.
Inks are used for various purposes by using this technique. Such purposes are not limited to the mere formation of beautiful color images such as photographs and business documents and extend to industrial purposes, for example, a purpose of printing postal markings (hereinafter also referred to as indicia) in large quantities and at high speed in the field of mailing business. The utilization of the ink jet recording technique in the mailing field is made not only in America and Japan, but also in various European countries. For example, in Germany, France and Switzerland, ink jet recording apparatus for forming blue indicia are put to practical use.
With the advancement of digital documentation in the mailing field in recent years, a mailing system making use of such indicia that information has been added thereto by using a 2-D bar code is put to practical use. The 2-D bar code makes it possible to achieve automated and labor-saved sorting and inputting operations and improve services for customers, because a great amount of information can be recorded at high density and read.
A fluorescent ink for mailing systems which can satisfy both properties of water fastness and fluorescence intensity comprises a water-soluble resin and a pigment is reported as a mailing ink in U.S. Pat. No. 6,176,908. In this mailing system, an indicia is printed on mail matter with the ink, and the indicia is read by a dedicated machine, whereby the postage, mailed district of the mail, recorder of the indicia, etc. can be known.
On the other hand, an ink comprising a cyan dye and a magenta dye having respective specific structures in a specific ratio is disclosed as a blue ink in Japanese Patent Application Laid-Open No. 2001-220529. This ink is said to be high in printing density and excellent in reliability on recording apparatus.
It has also been known to mix several kinds of coloring materials for representing an intended color as a print. For example, inks comprising both a black type color coloring material and a cyan type color coloring material are disclosed in Japanese Patent Application Laid-Open No. 2001-106946 and the like. However, the visually recognized color of all the inks disclosed is black, and no blue ink has been reported.
A recording apparatus, which is equipped with first and second electrodes, to which voltages different from each other can be applied, thereby inhibiting the generation of ink mist is reported in Japanese Patent Application Laid-Open No. H05-000518.